1. Field of the Invention
The invention relates to thread handling devices for use in sewing machine and more particularly to mechanism for pulling thread from a bobbin spool in a lock stitch sewing machine.
2. Description of the Prior Art
It is known to provide a lock stitch sewing machine with means for pulling thread from a bobbin spool for use in the formation of stitches, and it is usual for such thread pulling means to supply a constant amount of thread for each stitch regardless of the length of stitch called for. However, the feeding of constant amounts of bobbin thread regardless of stitch length requirements is a disadvantage in that it may result in stitches which are too tight and cause puckering of material being sewn, or in stitches, which are inadequately locked and tend to pull out the material.